Lactobacillus Acidophilus: Characteristics, Taxonomy, Morphology

Lactobacillus acidophilus is a species of lactic acid bacteria that is part of the microbiota of the intestine, mouth and vagina of humans, and the intestine of certain mammals. 
It also has a great variety of foods as a natural ecological niche, including milk, meat, fish and cereals.

Despite the name of its species “acidophilus”, which means affinity for acidity, this microorganism is able to tolerate acidic pH just like other species of the same genus.

L. acidophilus

In this sense, this microorganism generally resists gastric acidity and bile salts. Its survival rate in the gastrointestinal tract ranges between 2 and 5% and achieves sufficient concentrations in the colon (10 6 -10 8 CFU / mL).

Depending on the strain, its intestinal adhesion capacity, the favorable effects in terms of lactose digestibility and its ability to prevent diarrhea vary.

Article index

  • one


  • two


  • 3


  • 4


    • 4.1

      -Nutritional benefits

    • 4.2

      -Therapeutic benefits

    • 4.3

      -Industrial benefits

  • 5


Caract erísticas

The Lactobacillus acidophilus are microaerophilic and homofermentative.

Microaerophiles means that they grow well with low oxygen tension and 5-10% CO 2
While homofermentative means that they are capable of producing only lactic acid from the fermentation of sugars, specifically lactose.

Its optimum growth temperature is 37 ° C.

L. acidophilus  survives at pH 2.0 for a 2 hour incubation period and against 0.3% bovine bile salts.

It can be produced on a large scale, which is a property exploited by industry and can remain viable and stable, both in food and in the intestinal ecosystem.

This allows to establish that L. acidophilus meets all the important requirements according to FAO / WHO to be considered a probiotic bacteria.

L. acidophilus has rarely been involved in infectious processes, however among the few reported cases that have been described are abscesses, septicemia, and endocarditis.

The registered cases come from immunosuppressed patients, with some previous conditions such as short bowel syndrome.

Also in patients with central venous catheters or with heart valve disease and in premature newborns.


Domain: Bacteria

Division: Firmicutes

Class: Bacilli

Order: Lactobacillales

Family: Lactobacillaceae

Genus: Lactobacillus

Species: acidophilus.


Lactobacillus acidophilus are bacilli that turn purple on Gram stain, that is, they are Gram Positive. It does not form spores.

Nonviable bacteria can be stained Gram negative. They are usually seen isolated or forming palisades.

In Pap smears, this and other Lactobacillus can be seen and are normally reported as Döderlein’s Bacillus .

Regarding its structure, it is composed of a cell wall with characteristics corresponding to a Gram positive bacterium.

The peptidoglycan of the cell wall is made up of teichoic, lipoteichoic, lipoglycan, teicuronic acids and also contains a secondary polymer layer (SCWP).

Also, some strains have an additional envelope in their cell wall called the S-layer protein or surface layer (S & layer). 
It should be noted that this layer represents the first barrier between the microorganism and its environmental niche.

This protective layer could help maintain the shape and rigidity of the cell, as well as maintain stability and strength. 
It also allows accommodation and adherence to the intestinal walls.

Recently it has been discovered that it has a lytic activity on the wall of pathogenic bacteria, especially Gram negative ones, and 
It has a synergistic effect between the S & layer protein and nisin that inhibits growth and generates lysis of pathogenic bacteria, both Gram positive and Gram negative.


The benefits that Lactobacillus acidophilus offers are very varied, but can be summarized in three main ones: nutritional, therapeutic and industrial benefits.

The nutritional ones refer to the property that this species possesses to increase the bioavailability of certain metabolites in the intestine so that they are absorbed. In this way the nutritional status of the individual is favored.

Therapeutics are based on the usefulness they have for:

  • Reestablish the intestinal and vaginal microbiota when there is an imbalance in these areas.
  • Cholesterol metabolism.
  • Ability to suppress pro-carcinogenic enzymes.
  • Eliminate free radicals.
  • Suppress joint inflammation and synovitis.
  • Immunomodulator.
Industrialists refer to the uses that this bacterium has been given in food production.

-Nutritional benefits

Lactobacillus acidophilus, like other probiotic bacteria, intervenes in the digestion of food, by facilitating the breakdown of proteins in whole milk.

Thus increasing the bioavailability of nutrients such as zinc, iron, calcium, copper, phosphorus and manganese in the intestine.

Also during digestion, it helps the human intestine in the production of niacin, folic acid, vitamin B6 (pyridoxine) and vitamin K.

-Therapeutic benefits

Restores the intestinal microbiota

Consuming yogurt that contains Lactobacillus acidophilus can help prevent and counteract the problems of diarrhea and gastrointestinal bacterial infections.

For this they use several mechanisms:

The first is its ability to modify the balance of the intestinal microbiota by inhibiting the growth of undesirable bacteria by competing with them for the same nutrients, thus entering into competition.

In this way, the excessive development of pathogenic bacteria is controlled due to the decrease in nutrients.

Another mechanism used by Lactobacillus acidophilus is its ability to increase intestinal acidity through the production of lactic acid and acetic acid, which inhibits the development of many harmful bacteria, which do not support acidity.

Likewise, they have the property of producing substances called bacteriocins.

These substances work in a similar way to natural antibiotics, eliminating pathogenic microorganisms, especially Gram negative ones.

Maintains vaginal acidity preventing the colonization of other microorganisms.

Lactobacillus acidophilus  controls the population of Candida albicans Complex  in the vagina, limiting its excessive proliferation by inhibiting the adherence of yeast to vaginal epithelial cells.

Lactobacillus acidophilus does not act alone, but together with other species of the genus that are also part of the vaginal microbiota.

Among them: Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus jensenii and Lactobacillus iners.

Regulation of hypercholesterolemia

Some studies show that it can contribute to the deconjugation and separation of fatty acids by bile acids, which can later be recycled by the body.

Therefore, it participates in the regulation of cholesterol, helping to lower its plasma levels.

Anti-cancer action

It is related to the prevention of colon cancer and aging.

Lactobacillus acidophilus has been shown to decrease the proliferation of cancer cells and induce apoptosis (death) of these cells.

Free radical scavenging and anti-arthritic function

In relation to aging, it has been observed in animal models (rats) that the oral consumption of L. acidophilus eliminates free radicals from the liver, kidney and reproductive system, as well as improves the signs of arthritis.

Immunomodulatory action

Also Lactobacillus acidophilus is capable of enhancing the functioning of the immune system. 
It activates local macrophages and increases secretory immunoglobulin A (IgAs) production.

Likewise, it decreases the response to food antigens and modulates the cytokine profile.

In conclusion, the consumption of probiotics benefits the overall health of the individual, since they guarantee its balance.

-Industrial benefits

Lactobacillus acidophilus produces type II bacteriocins. 
This makes it an excellent biopreservative, as it prevents the proliferation of other microorganisms in food.

In addition,  L. acidophilus is used as a supplement in many food fermentation processes that contribute to a unique smell, taste and texture.

Likewise, Lactobacillus acidophilus is used for its beneficial effects in animal production specifically in chicks. Increases body weight gain and decreases fecal weight in these animals.


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